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DBMS_XPLAN.display_cursor shows wrong elapsed time on nested loops

User_HMTR3Aug 24 2018 — edited Aug 26 2018


I often have to display executions plans on Oracle 11 for tuning SQL purpose. After executing a SQL statement, I show the execution plan using the following query :

SELECT * FROM TABLE(DBMS_XPLAN.display_cursor(format=>'ALLSTATS LAST +cost +bytes'));

It works fine. But sometimes there is something wrong within the execution plan : on nested loops operations, I got sometimes an elapsed time that is bigger than the total elapsed time of the whole process. Here is an example :

Screenshot - 24.08.2018 , 15_59_22.png

I don't understand why. The query has spent exactly 1 minute 52 secs. So, the nested loops greather than 3 minutes are wrong.

Can you please help me understand ?


Best regards.


This post has been answered by Jonathan Lewis on Aug 25 2018
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Locked due to inactivity on Sep 23 2018
Added on Aug 24 2018